Production of polylactams



United States Patent 3,308,099 PRODUCTION OF POLYLACTAMS CharlesMermoud, Lyon, and Jean Abeille, St-Rarnbert LIle Barbe, France,assignors to Societe Rhodiaceta, Paris, France, a French body corporateNo Drawing. Filed Mar. 21, 1963, Ser. No. 266,826 Claims priority,applicsationlll rance, Mar. 29, 1962,

10 Claims. (cl. 260-78) This invention relates to the production ofsynthetic linear polyamides by the anionic polymerisation of' f lactams,and more especially to such polymerisation when carried out at atemperature below the melting point of the polyamide product.

The reactions involved in the production of synthetic linear polyamidesby anionic polymerisation of lactams""- have a very high velocity whenthe operation takes place above the melting point of the polyamide inquestion. In such a process, the catalysts normally employed areorganomagnesium complexes or alkali or alkaline earth metals orderivatives thereof, such as the oxides, hydroxas injection or extrusionof the polyamides in the molten state.

In order to accelerate the rate of reaction at these relatively lowtemperatures, various. compounds, generally known as co-catalysts, havebeen proposed, which, when .mosphere in order to avoidoxidation of thepolyamide added to the reaction mixture, permit the polyamide to beobtained in a comparatively short time and ata rate which issatisfactory for commercial operation.

Among the compounds that have been proposed as co catalysts are thosecontaining the active group:

A N-B I wherein A and B represent 0 --C=o, C=s, s N=0 eg N-acetylcaprolactam and also compounds capable of forming such derivatives byreaction with the lactam, such, for example, as acetyl chloride, aceticanhydride, and carbon dioxide gas.

Other compounds that have been proposed as cocatalysts includederivatives of a mineral 'or organic acid,

such as the esters, amides or nitriles, for example triphenyl phosphateor butyl stearate; and urea, thiour'ea and guanidine derivatives.

According to the present invention there is provided a process for thepreparation of synthetic linear polyamides by anionic polymerisation oflactams, wherein the polymerisation is effected in the presence of, ascocatalyst, a linear polyether of the general formula:

wherein X represents hydroxyl or an organic radical of valency p; each Rrepresents a hydrocarbon radical, which may be the same or differentthroughout the molecule; Y is hydrogen or a group inert to thepolymerisation reaction; 11 is an integer equal to or greater than'2;'and p is a positive integer.

for .the polyamide.

3,308,099 Patented Mar. 7 1967 Examples of suitable cocatalysts are:triethylene glycol, polyethylene oxides, HO[(CH O],,H, polypropyleneoxides, HO [CH (CH CH O ,H, polytetramethylene. oxides, HO[(CH O],,H,the condensation products of ethylene oxide with lauric alcohol, I

CH (CH O(CH CH O),,H lauric acid, CH (CH COO(CH CH O),,H, p-toluenepolypropylene oxides of formula:

H (OCH CH -O (C H O -(CH CH O H wherein a, b, and 0 represent positiveintegers.

The present process is applicableto all lactams which easily yieldlinear polyamides by anionic polymerisation, that is to say, in practiceit is applicable to those which contain at least 5 carbon atoms in theirring, and more especially w-caprolactam, capryllactam anddodecanolactam. The vlactams can be used separately or in ad-.

mixture, particularly with-N-substituted lactams, to form copolyamides.

The catalyst generally used is sodium, potassium or an organomagnesiumcomplex, and is preferably present in an amount between 0.1% and 3% byweight of the lactam, the precise amount depending on the nature of thelactam, the nature of the said catalyst and the viscosity desired Inorder that the new co-cataly sts may achieve their maximum efiiciency,it is preferred that-they should'be soluble at the polymerisationtemperature in the reaction mixture formed by the lactam and thecatalyst. The

. quantities used generally vary from 0.1 to 5%-by weight,

based on the lactam.

The reaction is preferably carried out in an inert at- .moreespeciallybetween 150 vC. and the melting point of the polyamide. Itwill be appreciated that the cocatalysts of the present inventionpossess their greatest utility when the reaction is carried out belowthe melting point of the polyamide product, sinceconventional cat-.alysts alone produce satisfactory results above this temperature.

The duration of the polymerisation reaction may be varied according tothe characteristics required in the final polyamide, and is generallybetween 4 and 12 hours. However, when the polyamide product is to beproduced as large lumps, the duration of the reaction is often in excessof 12 hours.

The viscosity of the resulting polyamides may be'controlled by varyingone or more of the following conditions: proportion of catalyst, and thetime and temperature of. the polymerisation. By these means very highintrinsic viscosities may be obtained. 1

Irrespective of the working conditions, the polymerisation yield is verygood: for example, with caprolactarn, it always exceeds The mechanicalproperties of the polyamide products are similar to those manufacturedwith the cocatalysts previously used, particularly the breakingresistance, and the resistance to shock and abrasion. Moreover, thepresent process has one particularly important advantage over thosepreviously used; namely that its products are substantially colourless,particularly when triethylene glycol is used as cocatalyst, whereas theprocesses employed hitherto yield products having a yellowish colour.

If it is desired, any suitable auxiliary agent such as fillers, pigmentsand plasticisers, can be added to the reaction products.

The invention is illustrated by the following examples in which partsare given by weight.

Example I 4 parts of triethylene glycol are added to 400 parts ofe-caprolactam. This mixture is melted and when the temperature is in theregion of 80 C., 1 part of sodium is added. The mixture is homogenisedby stirring and the temperature is raised to 180 C. An increase in theapparent viscosity of the composition is observed at the end of 1 hour20 minutes, and after heating for 2% hours, the composition iscompletely opaque. The product obtained after 4 hours at 180 C. has aninherent viscosity in m-cresol of 0.65 and melting point 217 C.

Example II 4 parts of triethylene glycol are added to 400 parts ofe-caprolactam. This mixture is melted and when the temperature is in theregion of 80 C., 1.7 parts of potassium (equivalent to 1 part of sodium)are added. The mixture is homogenised by stirring and the temperature israised to 180 C. A marked increase in viscosity is observed afterheating for 50 minutes, and in 2% hours, an opaque mass is obtained. Theproduct obtained after 4 hours at 180 C. has an inherent viscosity inm-cresol of 0.72 and melting point 217 C.

Example III 2 parts of polyethylene oxide molecular weight 280 to 310(polyglycol 300 H of Naphtachimie) are added to 200 parts ofe-caprolactam. This mixture is melted and, when the temperature is inthe region of 80 C., 1 part of sodium is added. The mixture ishomogenised by stirring and the temperature is raised to 180 C. Afterheating for 2% hours, the mass is completely opaque. The productobtained after 4 hours at 180 C. has an inherent viscosity in m-cresolof 0.75 and a lactam content of 3.6% and melting point 218 C.

By way of comparison, after 7 hours under the same conditions butWithout cocatalyst, a polyamide having an inherent viscosity in m-cresolof 0.46 is'obtained.

Example IV 2 parts of polyethylene oxide molecular weight 380 to 420(polyglycol 400 S of Naphtachimie) are added to 200 parts ofe-caprolactam. This mixture is melted and when the temperature is in theregion of 80 C., 1 part of sodium is added. The mixture is homogenisedby stirring and the temperature is raised to 180 C. After heating 3%hours, the mass is completely opaque. The produce obtained after 4 hourshas an inherent viscosity in m-cresol of 0.75 and a lactam content of8.9% and melting point 217 C.

Example V 2 parts of polypropylene oxide molecular weight 975 to 1075(propylene glycol 1025, Union Carbide) are added to 200 parts ofe-caprolactam. This mixture is melted and when the temperature is in theregion of 80 C., 1 part of sodium is added. The mixture is homogenisedby stirring and the temperature is raised to 180 C. After heating for 4hours 25 minutes, the mass is completely opaque. The product obtainedafter heating for 6 hours has an inherent viscosity in m-cresol of 0.71and melting point 217 C.

Example VI 4 parts of triethylene glycol are added to 400 parts ofs-caprolactam. This mixture is melted, and when the temperature is inthe region of 80 C., 1 part of sodium metal is added. The mixture ishomogenised by stirring and the temperature is raised to 160 C. Afterheating for 10 hours at 160 C., the product obtained has an inherentviscosity in m-cresol of 0.95, a lactam content of 6.3% and meltingpoint 219 C.

By way of comparison, under the same conditions but without cocatalyst,the polymerisation does not occur.

Example VII 2 parts of triethylene glycol are added to 200 parts ofe-caprolactam. This mixture is melted and when the temperat-ure is inthe region of C., 1.7 parts of potassium (equivalent to 1 part ofsodium) are added. The mixture is homogenised by stirring and thetemperature is raised to 160 C. After 1%. hours, a mass is obtainedwhich rapidly becomes opaque, and after heating for 4 hours, the productobtained has an inherent viscosity in m-cresol of 0.79 and melting point217 C.

Example VIII 2 parts of triethylene glycol are added to 200 parts ofe-caprolactam. The mixture is melted and when the temperature is in theregion of 80 C., 1.7 parts of potassium (equivalent to 1 part of sodium)are added. The mass is homogenised by stirring and the temperature israised to 150 C. An increase in the viscosity of the mass is observedafter 1% hours. After heating for 4 hours, a very white product isobtained which has an inherent viscosity in m-cresol of 1.18 and meltingpoint 221 C.

By way of comparison, under the same conditions but without cocatalyst,the polymerisation does not take place.

Example IX 2 parts of triethylene glycol are added to 200 parts ofe-caprolactam. This mixture is melted and when the temperature is in theregion of 80 C., 1 part of potassium is added. The mixture ishomogenised by stirring and the temperature is maintained at 150 C. for4 hours. The polyamide obtained is very white and has an inherentviscosity in m-cresol of 1.36 and melting point 222 C.

Example X 4 parts of triethylene glycol are added to 400 parts ofw-capryllactam. This mixture is melted and when the temperature reachesabout C., 1 part of sodium is added. The mixture is homogenised bystirring and the reaction mixture is brought to the temperature of 180C., which is maintained for 6 hours. The polymer obtained has asoftening point of 198 C., an inherent viscosity in m-cresol of 0.90.

Example XI 6 parts of a condensation product of ethylene oxide andlauric alcohol (molecular weight approximately 400) are added to 500.parts of e-caprolactam. This mixture is melted and when the temperaturereaches about 80 C., 1 part of sodium is added. This mixture ishomogenised by stirring and the temperature raised to 180 C. The productobtained after six hours heating at 180 C., which is polycaprolactam,has an inherent viscosity in m-cresol of 0.90 and melting point 219 C.

We laim:

1. Process for the production of a linear polyamide which comprisesheating a lactam of at least 5 carbon atoms under anhydrous conditionsat between C. and the melting point of the polyamide product in thepresence of an alkaline anionic catalyst together with, as cocatalyst,0.1 to 5% by weight of the lactam of a linear polyether of formula:

where X is hydroxy, lauryl, lauroyl, or N-p-toluene sulphonamide, each Ris independently selected from the class consisting of CH CH CH(CH )CHand (CH n is an integer equal to or greater than 2, and p is 1 or 2.

2. Process according to claim 1 wherein the said cocatalyst is a memberselected from the class consisting of triethylene glycol, HO[(CH O],,H,

and the condensation products of ethylene oxide with lauric alcohol andlauric acid.

3. Process according to claim 1 wherein the cocatalyst is triethyleneglycol.

4. Process according to claim 1 wherein the cocatalyst is HO[(CH O] H.

5. Process according to claim 1 wherein the cocatalyst is HO[CH(CH )CHO] H.

6. Process according to claim 1 wherein the cocatalyst is a condensationproduct of ethylene oxide with a compound selected from the groupconsisting of lauric alcohol, lauric acid, p-toluene sul-phamide andpolypropylene oxide.

7. Process according to claim 1 wherein the catalyst is selected fromthe group consisting of sodium and potassrum.

8. Process according to claim 1 wherein the cocatalyst 6 is soluble atthe reaction temperature in the reaction mixture formed by the lactamand catalyst.

9. Process according to claim 1, wherein the linear polyamide is made bythe polymerisation of w-caprylactam.

10. Process according to claim 1, wherein the linear polya-mide is madeby the polymerisation of e-caprolactam.

References Cited by the Examiner UNITED STATES PATENTS 2,241,321 5/1941Schlack 260-78 3,028,369 4/1962 Butler et a1. 26078 WILLIAM H. SHORT,Primary Examiner.

H. D. ANDERSON, Assistant Examiner.

1. PROCESS FOR THE PRODUCTION OF A LINEAR POLYAMIDE WHICH COMPRISESHEATING A LACTAM OF AT LEAST 5 CARBON ATOMS UNDER ANHYDROUS CONDITIONSAT BETWEEN 130*C. AND THE MELTING POINT OF THE POLYAMIDE PRODUCT IN THEPRESENCE OF AN ALKALINE ANIONIC CATALYST TOGETHER WITH, AS COCATALYST,0.1 TO 5% BY WEIGHT OF THE LACTAM OF A LINEAR POLYETHER OF FORMULA: